[Bug c++/85714] -Wimplicit-fallthrough and nested exhaustive switch statements with enum classes and return

[rs2740 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85714

--- Comment #4 from TC <rs2740 at gmail dot com> ---
[dcl.enum]p4:

The underlying type can be explicitly specified using an enum-base. For a
scoped enumeration type, the underlying type is int if it is not explicitly
specified. In both of these cases, the underlying type is said to be fixed.

p8:

For an enumeration whose underlying type is fixed, the values of the
enumeration are the values of the underlying type.